1. Field of the Invention
This invention relates in general to electric submersible pumps (ESPs) and, in particular, to an ESP thrust module with enhanced lubrication and temperature dissipation.
2. Brief Description of Related Art
Electric submersible pump (ESP) assemblies are disposed within wellbores and operate immersed in wellbore fluids. These wellbore fluids may be corrosive or toxic and were they to penetrate the electric motor portion of the ESP, would cause failure of the electric motor and thus the ESP. Thus, ESPs include sealing assemblies interposed between the electric motor and the pump portion of the ESP. These sealing assemblies prevent the flow or seepage of wellbore fluids into the electric motor. However, present sealing assemblies provide only limited sealing between the pump and the electric motor. If the primary seals fail, then the sealing assemblies and subsequently the electric motor will be inundated with wellbore fluids. Therefore, there is a need for an improved sealing assembly that provides additional redundancy.
The sealing assemblies also may include thrust bearings adapted to transfer the thrust generated by the pump in the opposite direction of the flow of wellbore fluids. Lubricating fluid is often interposed within the thrust bearings to allow a thrust runner coupled to an axial shaft within the thrust bearing to rotate relative to bearings supporting the axle. Operation of the thrust bearing generally cause this fluid to break down and wear over time. This is due in part to heat generated between the thrust runner and thrust bearing that causes a loss in viscosity of the lubricating fluid. The problem becomes exacerbated when the ESP is operated in subsurface/subsea wellbores. In these locations, the ESP can be subject to extremely high downhole temperatures. The high temperatures speed up the process of lubricating fluid breakdown. When the lubricating fluid breaks down, it may inhibit and even prevent operation of the thrust bearing, significantly decreasing the efficiency and life of the ESP. Therefore, there is a need for improved lubrication of thrust bearings within an ESP.